1. Field of the Invention
This invention relates to an image pickup apparatus including a solid-state image sensing device having a large number of pixels.
2. Background Art
In recent years, various image pickup apparatus capable of picking up an image in a wide dynamic range have been proposed (For example, refer to JP-A-2004-048445 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”)). JP-A-2004-048445 discloses the following image synthesis method: a high sensitive image and a low sensitive image less different in time and space are acquired using a solid-state image sensing device wherein each light reception cell is divided into a high sensitive light reception area and a low sensitive light reception area, an image quality degradation area of white splattering, black batter, etc., is automatically determined from one of the two images, the corresponding area is cut out from the other image in accordance with information of the image quality degradation area, and the cut-off image portion is combined with the portion of the image quality degradation area. Then, low-pass filtering is performed about all area of the composite image or the nearby area of the combined boundary for making the image smooth and then edge enhancement processing is performed.
In the method in the related art described above, a picked-up image based on the low sensitive light reception cells and a picked-up image based on the high sensitive light reception cells are partially cut and pasted to form one wide dynamic range composite image. However, since the low sensitive light reception cell has S/N ratio lowered relative to the high sensitive light reception cell, if they are partially combined into one, an unnatural image results. Although the low sensitive light reception cell and the high sensitive light reception cell are close to each other, they are placed at different positions and thus the picked-up image based on the low sensitive light reception cells and the picked-up image based on the high sensitive light reception cells differ slightly in time and space and an unnatural image results.
Processing of replacing an image quality degradation area of one image with an area of the other image corresponding to the image quality degradation area is performed, whereby it is made possible to correct white splattering, batter, etc. However, if output of the high sensitive light reception cell and output of the low sensitive light reception cell are saturated, such correction becomes difficult to execute.